What is the wave equation for the Casimir Effect and how was it derived?

[epislon58]

Hello, I am looking at the wave equation for the casimir effect and I was hoping if some could tell me what type of what equation is it and what techinque is used to derive it. The wave equation can be found here: http://en.wikipedia.org/wiki/Casimir_effect

Thank you

 

[UltrafastPED]

There is a footnote to the original paper by Casimir: http://www.dwc.knaw.nl/DL/publications/PU00018547.pdf